Tectonic slicing of subducting oceanic crust along plate interfaces: Numerical modeling

Jonas Ruh (1) , Laetitia Le Pourhiet (2) , Philippe Agard (2) , Evguenii Burov (2) , T. Gerya (3)

1 iSTeP - Institut des Sciences de la Terre de Paris
2 LSD - Lithosphère, structure et dynamique
3 Institute of Geophysics [ETH Zürich]

Multikilometer-sized slivers of high-pressure low-temperature metamorphic oceanic crust and mantle are observed in many mountain belts. These blueschist and eclogite units were detached from the descending plate during subduction. Large-scale thermo-mechanical numerical models based on finite difference marker-in-cell staggered grid technique are implemented to investigate slicing processes that lead to the detachment of oceanic slivers and their exhumation before the onset of the continental collision phase. In particular, we investigate the role of the serpentinized sub-crustal slab mantle in the mechanisms of shallow and deep crustal slicing. Results show that spatially homogeneous serpentinization of the sub-Moho slab mantle leads to complete accretion of oceanic crust within the accretionary wedge. Spatially discontinuous serpentinization of the slab mantle in form of unconnected patches can lead to shallow slicing of the oceanic crust below the accretionary wedge and to its deep slicing at mantle depths depending on the patch length, slab angle, convergence velocity and continental geothermal gradient. P-T paths obtained in this study are compared to natural examples of shallow slicing of the Crescent Terrane below Vancouver Island and deeply sliced crust of the Lago Superiore and Saas-Zermatt units in the Western Alps. This article is protected by copyright. All rights reserved.

Domaines: Sciences de la Terre

Jonas Ruh, Laetitia Le Pourhiet, Philippe Agard, Evguenii Burov, T. Gerya. Tectonic slicing of subducting oceanic crust along plate interfaces: Numerical modeling. Geochemistry, Geophysics, Geosystems, 2015, 16 (10), pp.3505-3531. ⟨10.1002/2015GC005998⟩. ⟨hal-01207648⟩